For spa and swimming pool pumps, two different speeds are needed. When such pumps are driven by a 2/4-pole motor, a 2-pole speed is needed to run the full-load operation, i.e. create a water whirlpool, and a 4-pole speed is needed to run a light load, i.e., circulate the water. Because of the nature of the pump loads, the 4-pole output power is about ⅛ of the output power of the 2-pole operation. A PSC motor has been used for the 2-pole operation and a split phase or capacitive-start motor has been used for both 4-pole start and 2-pole start operations. The 4-pole operation uses the main winding only. Thus, the 4-pole efficiency is low. For example, a 2.5 Hp may have a 77% efficiency for 2-pole operation and a 48% for 4-pole operation.
In other similar products, a PSC motor has been used for 2-pole running and a capacitive-start motor has been used for both 4-pole start and 2-pole start. Again, the 4-pole run uses the main winding only.
In yet other similar products, a PSC/PSC motor solution has been used with independent main and auxiliary windings for the 2-pole PSC running. It also uses independent main and auxiliary windings for 4-pole PSC running. This solution has shortcomings and limitations. When the 2-pole winding is in operation, the 4-pole winding is idle. When the 4-pole winding is in use, the 2-pole winding is idle. Thus, the motor's windings are not efficiently used.
In U.S. Pat. No. 5,825,111, for “Single Phase Induction Motor 4/6 Pole Common Winding Connection with Magnetic Motive Force Symmetrically Distributed,” co-invented and co-assigned with this application, a winding connection for a 4/6-pole PSC/PSC motor for a washer application is described. In this connection approach, a portion of the 4-pole main winding and a portion of 4-pole auxiliary winding become the 6-pole main winding and another portion of the 4-pole winding and another portion of the 4-pole auxiliary winding become the 6-pole auxiliary winding. It requires 11 leads and 7 single-pole double-through switches for switching between pole configurations.
U.S. Pat. No. 6,707,214, for “PSC Motor Having a 4/6 Pole Common Winding and Having an Additional 4-Pole Winding,” co-invented and co-assigned with this application, is an improvement for U.S. Pat. No. 5,825,111. With an additional 4-pole winding, the performance for both speeds improves without increasing the lead and switch numbers.
In U.S. Pat. No. 6,175,209, for “2/4-pole PSC Motor with Shared Main Winding and Shared Auxiliary Winding,” co-invented and co-assigned with this application, a winding connection for a 2/4-pole PSC/PSC motor for compressor application is described. In this connection approach, a 2-pole main winding becomes a 4-pole main winding and a 2-pole auxiliary winding becomes a 4-pole auxiliary winding through reconnection. The 2/4-pole main winding and the auxiliary winding are not 90 degree apart in space. The electrical angle between the 2-pole main and auxiliary windings is lower than 90 degree. The electrical angle between the 4-pole main winding and auxiliary winding is higher than 90 degree. The deviation from 90 degree for both represents a compromise in performance for both speeds. This approach requires 4 single-pole double throw switches for switching between pole configurations.
With the recent desire to increase energy conservation, there is a need to raise the 4-pole efficiency of water recreational pump motors. Also, many capacitive-start motors require a centrifugal actuator with the starting switches. A motor design which features a centrifugal starting switch is statistically less reliable than designs without it. Thus, there is also a need to develop such a motor which does not require a centrifugal starting switch and which does not require additional switches for switching between pole configurations.